Preparation method of monoclinic-phase lead tungstate

Abstract

The invention discloses a preparation method of monoclinic-phase lead tungstate, which comprises the following steps: in the stirring state, dropwisely adding a 0.001-0.01 mol / L soluble lead salt aqueous solution into a 0.004-0.02 mol / L soluble tungstate aqueous solution, continuing stirring for 5-60 minutes after finishing adding, thereby obtaining the reaction system, wherein the mol ratio of soluble lead salt to soluble tungstate is 1.24-5; and aging the reaction system at 5-45 DEG C for 66-82 hours, washing, carrying out centrifugal separation, and drying to obtain the monoclinic-phase lead tungstate. The preparation method of monoclinic-phase lead tungstate has the advantage of mild reaction conditions, and the preparation process i simple to operate. The raw materials are cheap inorganic salts; and the preparation process does not need any additive. Thus, the prepared pure monoclinic-phase lead tungstate product is clean, the pollution is low in the preparation process; and the invention lowers the production cost, and can easily implement industrial production.

Description

technical field [0001] The invention relates to the field of preparation of lead tungstate, in particular to a preparation method of monoclinic phase lead tungstate. Background technique [0002] Lead tungstate (PbWO 4 ) crystals have the characteristics of high density, large absorption coefficient, short radiation, and strong radiation resistance. They are widely used in fluorescent materials, optical fibers, dyes, etc., and can be used in quantum colliders and medical imaging. attention of many researchers and scientists. [0003] There are three main crystal structures of lead tungstate: tetragonal lead tungstate (mainly found in scheelite), monoclinic lead tungstate (mainly found in wolframite, also known as monoclinic lead tungstate) And high-voltage lead tungstate crystals, among them, tetragonal lead tungstate is widely distributed in nature and is easy to prepare in the laboratory. High-voltage lead tungstate crystals have also been synthesized by various methods,...

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Problems solved by technology

[0004] From the current reports, only a few researchers have prepared monoclinic lead tungstate by adding surfactants or organic solvents, for example, in 2008, Jinhu Yang et al. (references J.H.Yang, C.H.Lu, H.Su, J.M.Ma, H.M.Cheng and L.M.Qi, Nanotechnology, 2008, 19, 035608.) reported for the first time the monoclinic lead tungstate synthesized in the laboratory, the specific method is as follows: first a certain amount (such as 0.01 gram) of dextran sulfate -40 and a certain amount of sodium tungstate (such as 0.5mL sodium tungstate aqueous solution with a concentration of 0.1mol / L) were dissolved in a certain amount of water (such as 9ml), and then an equimolar amount of lead nitrate was added dropwise to the mixture (such as 0.5mL of lead nitrate aqueous solution with a concentration of 0.1mol / L), the monoclinic lead tungstate phase is obtained after the precipitation reaction, but this preparation method needs to use the additive dextran sulfate-40, and the dextran sulfate-40 The market price is high, and at the same time, the preparation process is relatively complicated, the cost is high, and there are problems of economic benefits

In the same year, India's Thresiamma George et al. (references T.George, S.Joseph, A.T.Sunny and S.Mathew, J.Nanopart.Res., 2008, 10, 567) reported that an equal amount of sodium tungstate and lead nitrate were mixed in A precipitation reaction occurred in polyethylene glycol-200 solvent to obtain monoclinic phase lead tungstate, but it can be clearly seen from the X-ray diffraction spectrum of the reported literature that the obtained product is a mixed phase tungsten of monoclinic phase and tetragonal phase. Lead acid, and organic solvents are used in the preparation process, which pollutes the environment, the preparation cost is high, and there are technical problems

In 2010, Chunhua Zheng et al. (References Chunhua Zheng, Chenguo Hu, etc. CrystEngComm, 2010, 12, 3277-3282, the author of this document has applied for a patent for the preparation method reported in the document, and the publication number of this patent application is CN101885511A) reported the preparation of monoclinic lead tungstate in mixed molten salt medium, the specific preparation process is as follows: 0.35 g of lead nitrate, 0.329 g of sodium tungstate and 3 g of mixed salt (LiNO 3 / KNO 3 =42.4:57.6) mixed, added to the reactor containing 3mL of ammonia water (pH=9), and then reacted at 160°C for 18 hours. Although this method obtained monoclinic lead tungstate, the X-ray It can be clearly seen from the diffraction spectrum that the obtained product is a mixed phase of monoclinic crystal phase and tetragonal crystal phase, and the preparation process requires high temperature and high pressure, high energy consumption, high cost, complicated process, and technical problems

Although this technical scheme uses additives, humidity, pH value, reaction time and other conditions to prepare lead tungstate nanomaterials with regular morphology, high crystallinity, and good fluorescence properties, the preparation process of this technical scheme is relatively complicated and requires the addition of additives. The nanomaterials are the tetragonal lead tungstate phases that exist more in nature and are easy to prepare in the laboratory. They do not involve monoclinic phase lead tungstate and there are technical problems such as relatively complicated preparation process and poor industrial production efficiency.

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